1. Field of the Invention
The present invention generally relates to combining Radio Frequency (RF) technology with novel micro-inductor antennas and signal processing circuits for RF telemetry of real time, measured data, from microelectromechanical system (MEMS) sensors, through electromagnetic coupling with a remote powering/receiving device. Such technology has many applications, but is especially useful in the biomedical area.
2. Description of the Prior Art
The prior art teaches capacitive sensors and switches that may be embedded within apparatus to perform remote sensing functions. However, the devices of the prior art are relatively complicated in structure and require the presence of a directly coupled power source. For example see the following U.S. Pat. Nos. 3,852,755; 4,857,893; 5,300,875; 5,335,361; 5,440,300; 5,461,385; 5,621,913; and 5,970,393.
The present invention teaches a microminiaturized inductor/antenna system for contact-less powering of an oscillator circuit providing an RF telemetry signal from biomicroelectromechanical (bio-MEMS) systems, sensors, and/or actuators. A miniaturized circuit inductor coil is printed on a dielectric substrate. The inductor coil behaves both as an inductor, which acts to charge a capacitive device as well as an antenna for transmitting a RF signal indicative of the level of charge of the capacitive device.
The micro-miniature circuit operates in two modes. In the first mode, the inductance coil forms a series resonant circuit with the capacitance of a capacitive MEMS device such as a pressure-sensing diaphragm of a MEMS pressure sensor device. In the second mode, the capacitive device produces an oscillating electrical current flow through a planar printed inductor coil. The inductor coil is equivalent to a helical antenna and hence loses power through RF radiation from the inductor. A remote RF receiving device may be used to receive the RF radiation, from the inductor coil, as a RF telemetry signal. The functional operation begins when an electromagnetic coupling energizes the circuit with a remote-transmitting device followed by oscillation of the circuit. Thus there is no direct or hard connection to the circuit by any power source.